1. Field of the Invention
The invention relates to an opening flap, in particular flue gas escape flap, comprising a frame; a flap that is articulated to the frame; a holding device for keeping the flap in a closed position; a lift arm which is mounted for pivoting about a first joint that is stationary relative to the frame; a principal energy accumulator, a first end of which is articulated to a second joint that is stationary relative to the frame, and a second end of which is articulated to the lift arm by a third joint at a distance from the first joint; and a secondary energy accumulator, a first end of which is articulated to the lift arm between the first and the second joint, and a second end of which is articulated to the flap. The invention further relates to an opening mechanism for an opening flap according to the invention.
2. Background Art
Flue gas escape flaps are employed predominantly for safety reasons in industrial buildings. They are supposed to be opened for fresh air and, possibly, light to enter; on the other hand, they must open automatically when for instance in the case of a fire or the like. Usually the flaps are held by a rope, by means of which they can also be shut. If the rope is loosened from its holding device at an easily accessible place, the flap will open automatically by means of an opening mechanism. By means of the rope it can be closed against the force of the opening mechanism. The rope is fixed to the flap by means of a holding device, for instance a lock with a safety fuse. This holding device unlocks in the case of fire so that the flap will open automatically. Gas springs are used as opening mechanisms for small flaps; they are articulated to the frame on the one hand and to the flap on the other. In the case of big flaps, it has been found that gas springs are not suitable. This is due to the fact that the opening mechanism must overcome not only the dead weight of the flap, but must be able also to lift comparatively heavy snow loads on the flap and force them aside upon pivoting beyond the proper upper dead center. Therefore, it has become a habit that pneumatically actuated piston-cylinder drives should be used instead of gas springs as opening mechanisms for big flaps; for opening, supply takes place from a pressure gas source, for instance a CO2 pressure cylinder.
DE 33 38 092 C3 describes a flap of the generic type, in which the additional energy accumulator is directly articulated to the lift arm, which results in extraordinarily bulky design. Moreover, the directions of application of force are rather unfavorable, opening heavy flaps being hardly, or not at all, possible.
It is an object of the invention to embody an opening flap of the generic type in such a way that big and heavy flaps can be opened by simple means.
According to the invention, this object is attained by the features which consist in that a double-armed lever is articulated to the lift arm by a pivot joint, to a first end, turned towards the principal energy accumulator, of which lever the secondary energy accumulator is articulated by its first end, and to a second end, turned towards the flap, of which lever is articulated a first end of a tie which is articulated by a second end relative to the frame. The measures according to the invention help attain that, at the beginning of the opening process when maximum load must be overcome, the principal gas spring exclusively or at least predominantly does the opening job, the secondary gas spring only serving as a forcing lever, transmitting the opening forces from the lift arm to the flap. The principal gas spring is completely extended only when the flap has been opened sufficiently far for a load of snow that might lie on it to have slipped off and any wind power has been overcome. Then the secondary gas spring takes the job of completely opening the flap as far as by an angle of approximately 140xc2x0 as against the closed position of the flap. This design is appropriate in particular for heavy flaps to be lifted. In keeping with the improved opening mechanism according to which the double-armed lever and the tie are arranged and designed such that, at the beginning of the opening motion of the flap, the first end of the secondary energy accumulator is moved counter to a direction of extension of the secondary energy accumulator, pivoting the double-armed lever, and according to which the pivoting motion of the double-armed lever reverses as the opening motion of the flap proceeds, provision is made for a type of transmission by means of which to accomplish a certain reducing effect at the beginning of the opening motion when major opening forces are needed and a certain multiplication as the opening motion proceeds and the required forces decrease.
The advantageous embodiment, according to which a stop is provided on the lift arm within the pivoting travel of the double-armed lever, ensures that the length of extension of the principal gas spring is restricted and the opening mechanism in the way of a transmission cannot tip over.
The further development, according to which F12xe2x89xa7F16, and in particular 6 F16xe2x89xa7F12xe2x89xa72 F16, and especially 10 F16xe2x89xa7F12xe2x89xa72 F16, applies to the extension force F12 of the principal energy accumulator in relation to the extension force F16 of the secondary energy accumulator, has regularly proved to be of advantage, favorably aiding in the specified repartition of forces.
With gravity acting on the flap in the final stage of the opening motion, the embodiment, according to which the secondary energy accumulator is a gas spring that is damped in the direction of extension, is as a rule of special advantage.
Furthermore, an opening mechanism is protected, including the features according to the invention.